From: Andy Shevchenko <andy.shevchenko@gmail.com>
To: Stuart Hayes <stuart.w.hayes@gmail.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>,
Austin Bolen <austin_bolen@dell.com>,
Keith Busch <keith.busch@intel.com>,
Alexandru Gagniuc <mr.nuke.me@gmail.com>,
"Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
Mika Westerberg <mika.westerberg@linux.intel.com>,
"Gustavo A . R . Silva" <gustavo@embeddedor.com>,
Sinan Kaya <okaya@kernel.org>,
Oza Pawandeep <poza@codeaurora.org>,
linux-pci@vger.kernel.org,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Lukas Wunner <lukas@wunner.de>
Subject: Re: [PATCH 2/3] PCI: pciehp: Wait for PDS if in-band presence is disabled
Date: Thu, 10 Oct 2019 08:37:02 +0300 [thread overview]
Message-ID: <CAHp75Vc1mZ7qxKPGaqDVAQ9d_UjNq9LJDEPWHQHaYCfw7vGrmA@mail.gmail.com> (raw)
In-Reply-To: <20191009200523.8436-3-stuart.w.hayes@gmail.com>
On Wed, Oct 9, 2019 at 11:05 PM Stuart Hayes <stuart.w.hayes@gmail.com> wrote:
>
> From: Alexandru Gagniuc <mr.nuke.me@gmail.com>
>
> When inband presence is disabled, PDS may come up at any time, or not
> at all. PDS being low may indicate that the card is still mating, and
> we could expect contact bounce to bring down the link as well.
>
> It is reasonable to assume that most cards will mate in a hotplug slot
> in about a second. Thus, when we know PDS only reflects out-of-band
> presence, it's worthwhile to wait the extra second or so to make sure
> the card is properly mated before loading the driver, and to prevent
> the hotplug code from disabling a device if the presence detect change
> goes active after the device is enabled.
> +static void pcie_wait_for_presence(struct pci_dev *pdev)
> +{
> + int timeout = 1250;
> + bool pds;
> + u16 slot_status;
> +
> + while (true) {
> + pcie_capability_read_word(pdev, PCI_EXP_SLTSTA, &slot_status);
> + pds = !!(slot_status & PCI_EXP_SLTSTA_PDS);
> + if (pds || timeout <= 0)
> + break;
> + msleep(10);
> + timeout -= 10;
> + }
Can we avoid infinite loops? They are hard to parse (in most cases,
and especially when it's a timeout loop)
unsigned int retries = 125; // 1250 ms
do {
...
} while (--retries);
> +
> + if (!pds)
> + pci_info(pdev, "Presence Detect state not set in 1250 msec\n");
> +}
--
With Best Regards,
Andy Shevchenko
next prev parent reply other threads:[~2019-10-10 5:37 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-09 20:05 [PATCH 0/3] PCI: pciehp: Do not turn off slot if presence comes up after link Stuart Hayes
2019-10-09 20:05 ` [PATCH 1/3] PCI: pciehp: Add support for disabling in-band presence Stuart Hayes
2019-10-09 20:05 ` [PATCH 2/3] PCI: pciehp: Wait for PDS if in-band presence is disabled Stuart Hayes
2019-10-10 5:37 ` Andy Shevchenko [this message]
2019-10-10 5:40 ` Andy Shevchenko
2019-10-10 20:37 ` Stuart Hayes
2019-10-11 6:49 ` Andy Shevchenko
2019-10-11 8:48 ` Andy Shevchenko
2019-10-11 9:05 ` Andy Shevchenko
2019-10-09 20:05 ` [PATCH 3/3] PCI: pciehp: Add dmi table for in-band presence disabled Stuart Hayes
-- strict thread matches above, loose matches on Subject: below --
2019-10-01 21:14 [PATCH 0/3] PCI: pciehp: Do not turn off slot if presence comes up after link Stuart Hayes
2019-10-01 21:14 ` [PATCH 2/3] PCI: pciehp: Wait for PDS if in-band presence is disabled Stuart Hayes
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CAHp75Vc1mZ7qxKPGaqDVAQ9d_UjNq9LJDEPWHQHaYCfw7vGrmA@mail.gmail.com \
--to=andy.shevchenko@gmail.com \
--cc=austin_bolen@dell.com \
--cc=bhelgaas@google.com \
--cc=gustavo@embeddedor.com \
--cc=keith.busch@intel.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-pci@vger.kernel.org \
--cc=lukas@wunner.de \
--cc=mika.westerberg@linux.intel.com \
--cc=mr.nuke.me@gmail.com \
--cc=okaya@kernel.org \
--cc=poza@codeaurora.org \
--cc=rafael.j.wysocki@intel.com \
--cc=stuart.w.hayes@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).